This invention relates to a fuel injector for supplying liquid fuel to an air inlet duct of a spark ignition engine, and more particularly to such an injector having a valve seat member on one face of which is formed an annular seating element for engagement by a solenoid actuated plate valve member, an orifice in the seat member through which fuel under pressure flows when the valve member is lifted from the seating element and a tubular outlet through which fuel flows from the orifice to the air inlet duct.
Such injectors are well known in the art and the physical dimensions of the injector have to meet a standard in order to allow interchangeability with injectors which employ different types of valve members. As a result the distance between the orifice and the end of the tubular outlet can be undesirably long when certain spray formations are required. For example, if two sprays are required for use with an engine having two air inlet ducts per cylinder, it is known to form two orifices which are angled to achieve the desired divergence. The extent of divergence is however limited without increasing the diameter of the tubular outlet, by the fact that the spray will impinge upon the wall of the outlet. As an alternative it has been proposed to provide a target at or near the end of the tubular outlet and to direct the fuel as a jet at the target. The target should divide the jet and also break up the jet to form the desired two diverging fuel sprays. In practice however it is found that the sprays are uneven unless the injector is produced to a very high and undesirable, degree of accuracy.
With other injectors it is desired to produce a single busy spray, that is to say a spray which has a large cone angle. The fact that the orifice is spaced from the end of the tubular outlet limits the degree of spread of the spray and if a conical target is used the same problem is encountered as described above namely that the injector must be produced to a very high degree of accuracy in order to form an even spray.